Machine tools such as an edge grinding apparatus include at least one grinding wheel, at least one rotatable holder for a blank, and at least one CNC device for controlling the grinding of the blank according to selected specification. The CNC machine tool may include a multi-axis, linear (X, Y axis) holder instead of a rotatable holder. In either case, a cutting tool moves relative to the blank or workpiece under the control of a programmable controller, including a computer program. The cutting tool is not restricted to standard turning or milling cutters, but also includes all mechanical, electronic and/or electro-mechanical devices used to modify the shape and/or properties of the workpiece. Examples of cutting tools include: end-mills, turning tools, grinding wheels, laser cutting beams, plasma beams and punch tools.
In a standard CNC glass grinding machine, an operator must adjust the CNC parameters to allow the CNC machine to grind the part where it is located on the machine. This can be a slow process and is difficult for many operators to master. The prior art process requires the operator to grind a part, check the part for even grind then adjust the X, Y and rotation offset parameters on the CNC control to move the CNC program to match the part location. This normally requires many iterations at about 30 to 60 seconds per pass. Operators can easily make errors that may damage the machine or grinding tool and make the process take much longer. Also, operators may make imperfect adjustments during set up causing excess tool wear, lower throughput and lower yields.
U.S. Pat. No. 5,588,899 discloses one solution to this problem. The apparatus of this patent is an opto-electronic device for positioning eye glass or spectacle lenses in a CNC grinding device. The opto-electronic detecting device includes a CCD (charge coupled device) camera, wherein the CCD camera is connected to a first control unit that includes an electronic picture processing and evaluating system cooperating with a second control unit. The CCD camera detects markings on the lens blank and the first and the second control units cooperate for positioning the lens blank on the holder. The system requires the manufacturer of the lens blank to mark each blank. If the blanks are not premarked, a separate marking is necessary.